Cytologic Interpretation of Melanotic Neuroectodermal Tumour of Infancy Involving Cranial Bones: Clue to Diagnosis

Melanotic neuroectodermal tumour of infancy (MNTI) is a rare, benign but locally aggressive neoplasm of infants commonly affecting the maxilla. It can also involve other areas like skull, mandible, brain and epididymis. The tumour comprise of dual populations of cells like small, basophilic neuroblast like cells and large pigment laden epithelial cells arranged in tubular and pseudoglandular pattern. The proportion of two components varies and therefore the diagnosis can be difficult in absence of the large cells. We describe the cytologic, histologic and immunohistochemical findings in a case of MNTI involving left side orbit with frontal, temporal and parietal bones. The cytologic interpretation could be made due to the suggestive clinical and radiologic findings and detection of large epithelial pigmented cells on thorough searching. The neuroblast like cells was positive for Neuron specific enolase, large cells for HMB-45 and Pan CK. Both the cellular components were negative for desmin. This case report is presented due to its rarity and also to aid the surgical pathologists in diagnosis where the findings are not too straight forward.